The invention concerns food products with a fibrous texture, obtained mainly from whey proteins, a manufacturing process by extrusion baking of these products and a manufacturing installation for application of the process.
Processes for the manufacture of dairy products by continuous extrusion are already known.
Document EP-A-727 138 describes one such extrusion process by means of which cheese or cheese products are obtained from a curd or milk fraction resulting from ultrafiltration of milk.
The process is comprised of the following stages: introduction of raw materials, transfer into a barrel with at least one zone in which the temperature is between 60xc2x0 and 120xc2x0 C. involving blending, texturing and baking. This process gives rise to products with stretched structures whose fibres have a diameter that is generally greater than 0.1 mm and in the order of millimeters.
Document WO-96/34 539 describes a process used to obtain a textured protein matrix containing a dispersion of inclusion bodies.
These products are obtained by means of a high-temperature extrusion process, notably at temperatures of 125 to 160xc2x0 C. High temperatures such as this lead to the destruction of the initial protein mixture. The products obtained include protein fibres which are stable after cooling.
This document essentially describes the use of vegetable proteins such as soya. Document WO-96/25051 describes a process for the manufacture of a soft or semi-soft fibrous cheese. The fibrous mass is obtained after extrusion of the curdled milk.
These processes do not allow a cheese or milk mixture to be used to obtain a product with an extremely fine fibrous structure, comprising fibres whose sizes are in the range of xcexcm to 0.1 mm, noticeable when the product is chewed and conferring on it original organoleptic characteristics.
Document US 4,156,028 also describes a process for the manufacture of fibre products whose fibres have diameters in the order of 100 xcexcm for example. However, these products are obtained by a technique which involves dissolution followed by a coagulation bath; the principles and materials of this technique are considerably different from extrusion baking which brings together specific pressure and temperature features. The products obtained do not have a ramified network structure such as that described below.
To this end, a first aspect of the invention proposes a product obtained by extrusion baking of a mixture of dairy or cheese origin. This product has a fibrous structure with a network of macroscopic fibres whose diameters are in the order of 0.1 mm to 1 mm, ramified into microscopic fibres with diameters in the order of 1 xcexcm to 0.1 mm, the dry matter in the product being at least partially obtained from whey.
The dry matter in the product typically comprises 30% to 100% of dry matter originating from whey.
The product consists of 15 to 50% of dry matter and typically 25 to 40%. The dry matter of the product consists of at least 35% of total proteins.
The dry matter originating from whey includes isolated and/or concentrated proteins, and/or dried whole whey, and/or dried whey fractions such as lactose, milk fats, lactoferrin, calcium or other milk minerals or fractions.
According to one application, the product contains, in addition to whey proteins, other protein fractions such as casein or caseinates, cheese, dried or concentrated milk, with dry matter from the product preferably comprised of at least 10% casein.
According to another application, the product contains, in addition to whey proteins, non-dairy proteins chosen from among concentrated or isolated vegetable proteins, especially wheat, soya or pea gluten, liquid or dry egg white, with non-dairy proteins representing 0 to 70% of the mixture""s dry matter, and preferably 20 to 50%.
According to a second aspect, the invention concerns a food preparation incorporating a product in keeping with the description above added to various ingredients chosen from among cheeses, milk and derivative products (yoghurt, milk cream, milk powder, fromage blanc, butter), cereals, starches, flour, semolina, fruits and dried fruits, spices, seasoning, fats, flavouring, sugar-containing ingredients (sugar, honey . . . ), pieces of meat or fish or vegetables, so as to form ready-made meals, children""s snacks, sandwiches, snack foods, breakfast products, burger- or sausage-shaped cheese products, vegetarian products, spreads, pate, cooking ingredients . . .
According to one application, the food preparation has a matrix comprised of fibres or bundles of fibres with sizes in the range of mm or xcexcm, with the preparation having dimensions in the order of a few centimetres.
The preparation undergoes mechanical forming, metering, shaping in moulds or piping then pasteurised and sliced. The preparations obtained can be decorated, stamped, cooked or pre-cooked, pasteurised, sterilised and packaged.
According to one application, the preparation contains a product in accordance with the description above which encloses a dairy or non-dairy filling product.
According to another application, the preparation contains a product in accordance with the description above enclosed by a dairy or non-dairy coating product.
The preparation can also include salts, spices, seasoning and flavouring, oil or other fats, an acidity corrector such as lactic acid.
According to a third application, the invention concerns a process for the manufacture of products with a fibrous structure comprised of the following steps:
a) introduction of raw materials containing whey proteins into an extruder with at least one screw;
b) transfer of raw materials from one end to the other of the extruder barrel, adjusting the screw(s) and temperature within the barrel such that raw materials successively undergo a mixing and heating step up to a temperature of about 130xc2x0 C., followed by a melting step with an increase in temperature of the material to above 130xc2x0 C., generally between 140xc2x0 C. and 200xc2x0 C., and an increase in pressure to between 0 and 50 bars, such that plasticization of the transferred material takes place, especially of whey proteins;
c) extrusion at the far end of the barrel of the material obtained after plasticization through a die adapted for texturization, shaping and cooling the material such that a product with a fibrous structure is obtained.
Cooling takes place in the die to a temperature of 100xc2x0 C., possibly even between 80xc2x0 C. and 10xc2x0 C., and consists of an initial cooling phase in an uncooled zone in the die at the outlet of the barrel, followed by a second cooling phase in a cooled zone of the die. The first cooling phase corresponds to an alignment zone of the melted mixture which is in a viscous state and has a viscosity of 1000 to 500,000 centipoises while the second cooling phase corresponds to a change of state from the viscous state to the solid state, the linear flow rate of the product at the outlet of the die being in the order of 2 to 10 m/min.
Heating to 130xc2x0 C. in step b) is gradual or in stages.
The temperature can be adjusted during the process to modify the texture of products.
The mixture placed in the extruder is in the form of a powder, with all the required water added prior to the melting step, or in liquid or paste form.
According to one application, the whey proteins originate from whey protein concentrates or isolates which are 50 to 90% pure, preferably 70 to 80% pure, and also contain lactose, fats, minerals, secondary proteins of the casein macropeptide type.
The process also includes a cutting step at the outlet of the die such as chopping, slicing, crushing, tearing, shredding or similar to obtain chopped fibres forming flakes or bundles.
According to one application, it includes a step where the product is dried at the outlet of the die after cutting to produce rehydratable fibres for food preparations if need be.
The process can also include a culinary reconstitution step using chopped fibres mixed with various ingredients such as cheese, milk and derivative products, cereals, starches, flour or semolina, fats, spices, seasoning and flavouring.
It can also include a shaping step comprised of mechanical forming processes using a shaper or moulds or piping followed by pasteurisation and slicing, with the products obtained undergoing at least one of the following steps: decoration, coating, stamping, filling, frying, baking, pasteurisation, sterilisation, packaging.
According to one application, the material transferred to the die is filled with a filling product during the extrusion step, added through the coextrusion valve opening into the die.
The filling product can be obtained by means of an extrusion process.
According to a fourth aspect, the invention concerns a manufacturing installation for the application of the process presented above comprised of a screw extruder with two very similar interlocking screws which rotate in the same direction or in the opposite direction inside a horizontal barrel, a filling device attached at the near end of the barrel, fitted with one or more metering devices for metered flow of the mixture at a predetermined rate, an extrusion die located at the far end of said barrel, thermal treatment assembly for fine-tuning the temperature within the barrel and extrusion die, said barrel being comprised of:
a first zone for supply of the product formula;
a second zone for mixing, moisturisation where this is required, and heating the material up to a core temperature of at least 130xc2x0 C.;
a third zone for melting, increasing the temperature of the material to over 130xc2x0 C., generally between 140 and 200xc2x0 C. and pressure of the material to between 0 and 50 bars, depending on the composition of the formula, in which protein plasticization takes place, especially of whey proteins.
The second mixing and heating zone consists of 2 to 5 units, the third melting zone comprises 1 to 3 units, with a screw length to screw diameter ratio of about 10 to 33, typically between 25 and 33.
The extrusion die includes a first uncooled zone adjacent to the near end of the screw extruder, followed by at least one cooling zone, corresponding to an alignment zone for fibres in a viscous state and a change-of-phase zone from the viscous to solid state.
The die is connected to the barrel by means of at least one, and typically two, adapters. The first adapter has one or two perforations through which the melted and plasticized material is extruded; the second adapter is located between the first adapter and the extrusion die and its function is to balance materiel pressure and flow rate.
The extrusion die has an internal shape that is adapted to the final product, with size parameters designed to allow cooling of the melted and plasticized material to 100xc2x0 C., possibly between 80 and 10xc2x0 C. Its inner surface has a controlled roughness in order to exert shear forces on the product during the cooling process, the combination of cooling and shear forces leading to continuous.
Texturizaton of the cooled material to form fibres.
The installation can include an extrusion pump located, for example, between the first or second interface and die for steady supply to the die in order to stabilise product flow. This is often a gear pump whose body can be reheated by electrical resistances in order to maintain a melted and plasticized mass at the required temperature.
According to one application, a coextrusion valve opens into the extrusion die.